BACKGROUND: The nursing practice of avoiding dependent loops in the tubing of chest drainage systems because such loops may impede drainage and alter the intrapleural pressure is not research based. OBJECTIVES: To determine if the volume of fluid drained and pressure vary when the chest drainage tubing is straight, coiled, has a dependent loop, or has a dependent loop that is periodically lifted and drained. METHODS: A repeated-measures design was used. For each tubing position, 500 mL of fluid was infused into the pleural space of 8 adult pigs during 45 minutes. The volume of fluid drained and the pressure at 2 locations within the drainage tubing were measured for 1 hour. RESULTS: After 60 minutes, significantly less fluid (least significant difference test, P = .03) was drained with the dependent-loop tubing position (65 mL) than with the other 3 positions. However, the amount of fluid drained was not significantly different among the lift and drain (250 mL), coiled (301 mL), or straight (337 mL) tubing positions. Throughout the entire study, pressure at the connection between the chest tube and the drainage tube was significantly higher (least significant difference test, P = .003) for the dependent loop with and without periodic lifting and draining. CONCLUSIONS: Straight and coiled tube positions are optimal for draining fluid from the pleural space. If a dependent loop cannot be avoided, lifting and draining it every 15 minutes will maintain adequate drainage.
BACKGROUND: Maintaining a chest drainage tube in a position that is free of dependent loops, as is commonly recommended, can be very difficult. Is there a beneficial effect on the patient's outcome when the drainage tubing is free of dependent loops? OBJECTIVE: The purpose of this study was to determine, under controlled laboratory conditions, (1) what are the differences in drainage with tubing in straight, coiled, or dependent-loop (with and without periodic lifting) positions and (2) what are the differences in pressure with each of the four tubing conditions? METHODS: In laboratory simulations, pressure and drainage were observed in a chest tube drainage system that was connected to a glass bottle simulating the lung. Pressure and drainage were measured for 1 hour with the drainage tubing placed in straight, coiled, and dependent-loop positions. For the periodic lifting condition, the dependent loop was lifted and drained every 15 minutes. RESULTS: We found no differences in pressure or drainage between straight and coiled positions of the drainage tubing. However, with the dependent-loop position, pressure at the "lung" side increased from about -18 cm H2O to as high as +8 cm H2O. Drainage dropped to zero without tube lifting. When the tube was lifted and drained every 15 minutes, there was no difference in drainage with the tubing in the straight or coiled positions. CONCLUSION: Findings support recommendations to maintain tubing free of dependent loops by placing tubing in straight or coiled positions. Frequently lifting and draining a dependent loop will provide the same total drainage amount as maintaining the tubing in a straight or coiled position, but pressures may be altered sufficiently within the tube to exceed recommended levels.